378 IOWA ACADEMY OP SCIENCE 



4. Not thin, wafer-like and cream-colored. 

 5. Angular or angles distinct. 



6. Very light straw-colored with about 9 rounded 



longitudinal ridges (fig. XXVIII) 



Anthemis arvensis L. 98 



6. Not light straw-colored. 



7. Distinctly square in cross section, very dark 



brown to black. 



8. Angles acute, base drawn into an attenuate 



point almost uniform in diameter except at 



base, pappus capillary, over 1.8 mm. long. . 



Eupatorium perfoliatum L. 82 



8. Angles not acute, pappus of chaffy bristles, 

 surface hairy, not uniform in diameter, te- 

 trahedonal, under 1.8 mm. long (fig. IX).. 



Galinsoga parviflora Cav. 95 



7. Not distinctly square in cross section. 

 8. Plano-convex or concavo-convex in cross sec- 

 tion. 

 9. With 2 to 5 rows of frail spines on convex 

 surface, longitudinal ends not attenuate, 



lines pronounced (fig. XXX) 



Daucus Carota L. 61 



9. Without longitudinal rows as above, ends 



attenuate Digitaria sanguinale Scop. 1 



8. Not plano-convex or concavo-convex with lon- 

 gitudinal striations. 

 9. Cone shaped, with numerous gray hairs 

 and pappus of chaffy bristles (fig. IX) 



Galinsoga parviflora Cav. 95 



9. Not cone shaped or hairy. 



10. With longitudinal ridges or angles. 

 11. Comparatively thick set, dark, see de- 

 scription. .. .Verbena urticaefolium L. 68 

 11. Comparatively slender and light (fig. 



XI) Verbena hastata L. 69 



10. Without marked longitudinal striations. 



11. Surface finely reticulate 



Plantago major L. 77 



11. Surface granular, not reticulate 



Plantago Rugelii Dene. 78 



•".. Not angular. 

 6. Surface shining. 



7. Not at all uniform in diameter. 

 8. Uniform in shape, one end pointed, usually 

 with a whitish triangular appendage (fig. 



XXV) Prunella vulgaris L. 71 



S. Not uniform in shape. 



